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T O P I C R E V I E W

Robert Pearlman

NASA release

Spacewalk Mishap Investigation Board Report

NASA today (Feb. 26) released the findings [PDF] of an investigation into the July 2013 spacewalk at the International Space Station when water built up in astronaut Luca Parmitano's spacesuit helmet.

Soon after the incident, NASA created a Mishap Investigation Board to identify factors that may have contributed to the incident and recommend changes that could be implemented to prevent a similar situation from occurring again.

This safety investigation ran concurrently with an engineering study into the equipment failure.

NASA is concluding the mishap investigation and will share the board's detailed report of evidence and lessons learned with human spaceflight stakeholders inside and outside the agency. Information from the report will be integrated into the engineering investigation and directly benefit the ongoing search for a root cause.

Robert Pearlman

NASA release

Summary of Findings

The Mishap Investigation Board (MIB) sought to determine if there were ways to prevent this mishap from re-occurring, if there were ways to have minimized the risk to the crew once it occurred, and if there were ways it could have been prevented before it occurred.

The MIB determined that the causes for this mishap evolved from:

Inorganic materials causing blockage of the drum holes in the EMU water separator resulting in water spilling into the vent loop.

The NASA team's lack of knowledge regarding this particular failure mode, which led to a delay in recognizing the severity of the event when it occurred.

Misdiagnosis of this suit failure when it initially occurred on [the preceding] EVA 22.

The MIB determined that the space suit actually suffered the same failure at the end of EVA 22, performed a week earlier, and this event was not properly investigated which could have prevented placing a crew member at risk a week later during EVA 23.

Summary of Causes

Three Proximate causes were identified contributing to the severity of the event:

The ISS Program conducted EVA 23 without recognizing the EMU failure which occurred on EVA 22.

EMU 3011 Helmet had a large quantity of water during EVA 23.

Flight Control Team/Crew did not terminate EVA 23 as soon as water was reported in the helmet.

Ultimately these (1 and 3) were caused by five Root Causes:

Program emphasis was to maximize crew time on orbit for utilization.

ISS Community perception was that drink bags leak.

Flight Control Team's perception of the anomaly report process as being resource intensive made them reluctant to invoke it.

No one applied knowledge of the physics of water behavior in zero-g to water coming from the PLSS vent loop.

The occurrence of minor amounts of water in the helmet was normalized.

Kocmoc

Thanks for the summary, Rob. What I don't understand is where the silicates that caused the clogs came from. Did you get that answer?

------------------Cathleen S. Lewis

Robert Pearlman

Here is what the report says regarding the source of the contamination:

The source of the inorganic materials blocking the water separator drum holes had not been experienced during an EVA before and is still undergoing a concurrent investigation. The results of this investigation will ultimately lead to resolution of this issue; however, since the concurrent investigation into the source of the debris is expected to continue for many months, the MIB does not yet have the required data to determine the root causes of the contamination source, which must ultimately be determined to prevent future mishaps.

During a media telecon this afternoon, station program manager Michael Suffredini said that he expects the investigation into the root cause of the contamination to be resolved by June (and they are currently working towards a succession of planned spacewalks to pick up in late July or early August).

Here is what Suffredini said about the root cause:

We don't have root cause, but we have a most likely cause at this point. It is quite possible that it was a combination of events. One, a uniqueness of the subliminator in the suit 3011 and the possibility it might have been producing more silicates than other subliminators. Silicates are pretty common in a number of areas in the suit and it doesn't come off in large parts. On the blocked port, it actually comes off at the molecular level and then it nucleates in areas where you have the centrifuge working.

So this was a unique combination of a high-level of the silicate being in an area where you have the right environment for it to form into larger particles to cause blockage. So the team believes it is a combination of either that and the filter that we use to clean the water loops regularly on the suits. One of those filters may have been pre-contaminated and not able to perform the job of scrubbing out the silicates. A combination of those two events probably led to having the high-level of silicates in 3011 and eventually lead to the blockage of the ports.

Headshot

What is the point of the redactions?

Is there proprietary design/operational information that NASA believes should not be made public? I mean a few Russian cosmonauts have used our suits, heck the suit in question was being worn by an Italian astronaut when the event occurred, so what gives?

We all know that the minute some people see all these blacked-out areas, they start yelling cover-up and conspiracy. I am surprised that NASA would risk this.

Robert Pearlman

The redactions are due to International Traffic in Arms Regulations (ITAR). According to NASA, some of the technologies cannot be exported outside the U.S. per State Department restrictions.

Using and wearing a suit is different than distributing the technical details of how one works.

Headshot

I understand, thanks for the clarification.

JBoe

NBC Nightly News just reported the findings and also the aging equipment of NASA and the 30+ year old space suit design. Williams also stated that NASA has only 12 suits in its inventory.

Robert Pearlman

The shuttle and space station extravehicular mobility units (EMU) are comprised of components (e.g. hard upper torso, lower torso) that are mix and match.

So when someone says there are 12 spacesuits in inventory, they are referring to the limiting component; in this case, the Portable Life Support System (PLSS). NASA has 12 flight-worthy PLSS backpacks (four of which are currently on orbit).

To quote Chris Hansen, who chaired the Mishap Investigation Board, "Nothing in our investigation pointed to aging issues of the suit."

Rather, he said, it was more an issue of how the suits are being used now, as opposed to how they were used during the shuttle-era. Previously, the suits weren't outfitted with filters as they would be cleaned between flights. Quoting Suffredini:

We re-certified the suits to be on orbit for six years and to do 25 EVAs. In the process of doing that, there were a number of components that we looked at and replaced. The PLSSs themselves are basically refurbished. So the PLSSs and the suits themselves are really in great condition.

JBoe

Robert, thanks for clarifying. It was a little misleading for NBC News to generalize. It does make sense what you stated regarding the mix and match of components. Besides, most astronauts have suits fitted to them or suits that can be fitted in orbit which would create "more of an inventory."

Kocmoc

The news media (Rob, as usual, you are excepted) has been harping on the age of the suits issue for a while. I have tried to explain that design age does not equal materials age, that components have been upgraded over the course of decades and that the suit is an integrated part of the spacecraft.

The shift from use on the Shuttle to the ISS is an interesting engineering problem of substituting one set of maintenance protocols for another. It will be interesting to learn that what impact this will have on the design and maintenance protocols for the Z suits under development at JSC. I am assuming the new PLSS will not reply on LiOH scrubbers, but they might have to isolate the pump systems for easy swaps.

NavySpaceFan

I hoped never to have seen the phrase "normalization of deviance" again in a NASA report. Twice was too much.